Yeah, thats what will happen if you partition using the disc.
Does that mean you have a drive C and D? (C being the 10gb partition) (and you have another 90 on D?)
In that case, I guess when you boot up windows you get a choice of which operating system to run which can get a bit confusing. You can stop this:
Start, Control Panel, System, Advanced tab, then find startup and recovery at the bottom and go to settings. You'll now get another menu, press where it says edit to change how the computer boots. (beware though, doing this wrong can stop the pc booting into windows):
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Syste m 1" /fastdetect
multi(0)disk(0)rdisk(0)partition(2)\WINDOWS="Syste m 2" /fastdetect
multi(0)disk(0)rdisk(0)partition(3)\WINDOWS="Syste m 3" /fastdetect
multi(0)disk(0)rdisk(0)partition(4)\WINDOWS="Syste m 4" /fastdetect
(this is how mines set up) the default one is the one that boots after 30 seconds is over, and is usually the one you choose to get to windows. If you are not sure, restart and check which one you go to, to get the 10gb drive (if it makes it easier to remember you can change whats in the brackets "" to something else) and then delete the other one from the list after it boots again, being careful not to delete the wrong one by mistake. (The only reason I have 4 is because I have 4 partitions instead of your 2).
On mine you can see it is set to boot default into partition 1 which is "system 1".
If the default is set to the same one you deleted, you'll need to just simply change the partition(?) in brackets to the one that is left
After that is done you go to file save and then when you restart since there is only one left to boot from, you won't get this menu again asking you to select one.
You could then format drive D (one with 90gb left) (Leaving the 10gb one okay) in Windows (though make backups if you've written anything to it)
Right click My Computer and go to Manage, on the side tabs, choose 'disk management'. Find the second partition (90gb) which will be a fake drive (because you only have 1) and right click it and go to Format. Then simply follow the instructions to wipe it, choosing NTFS on the list which is more suited to WinXp
This should work for you